The invention relates to a linear drive having the features of a guide tube which has a longitudinal slot passing through its wall and in which a piston is mounted displaceably in the longitudinal direction.
Linear drives known from practice are so-called linear modules, in which a slide or piston is moved in an elongate, laterally slotted guide tube via a pressure medium or pull means. The slide or piston is connected firmly to a web which passes through the longitudinal slot provided in the guide tube and which, if appropriate, in conjunction with a slide mounted externally on the guide tube, serves as a driven member.
Although this linear drive is provided simply for generating linear movements, there can occur, depending on the type of force generation and depending on the type of connected load, forces which act laterally on the web and which possibly bring the web into contact with the flanks of the longitudinal slot provided in the guide tube. This happens, for example, when loads engaging laterally on the web are not absorbed by additional, sufficiently rigidly designed guide means.
Moreover, a force acting laterally on the web can occur when a screw-spindle mechanism is provided as a pressure medium or pull means acting in the guide tube. Even when the external load is purely linear, this screw-spindle mechanism exerts a torque on the web which is thus pressed toward one of the two flanks of the longitudinal slot. When the web consequently touches the particular flank and executes a linear movement, it is possible for the flank of the longitudinal slot to be damaged thereby.
German Offenlegungsschrift 3,429,783 discloses a linear-drive cylinder actuated by pressure medium, which has a guide tube closed off on both sides and possessing a longitudinal slot in which a flexible sealing-off band is held fixedly. A piston is mounted slidably and in a sealed-off manner in the guide tube and passes with a web through the longitudinal slot. The linear-drive cylinder is provided on its outside with a slide which is designated as a guide plate and which is guided on specifically provided rails in the longitudinal direction of the linear-drive cylinder. The web passing through the longitudinal slot is connected firmly to the slide.
So that forces acting laterally on the driven member of the linear-drive cylinder can be kept away from the web, the slide displaceably mounted on the outside of the linear-drive cylinder has been provided, this signifying additional outlay in terms of production.